1. Field of the Invention
This invention relates to flame retardant thermally insulating material and to a process for providing a flame retardant thermal insulation between at least two spaced-apart surfaces.
2. Description of the Prior Art
In the interests of energy conservation it has become common and desirable to insulate buildings in order to minimize heat loss. Various means are employed to achieve such insulation, and new buildings tend to incorporate some or all of them as an integral part of their design. Existing buildings which do not incorporate adequate thermal insulation in their original structure may be modified in various ways, e.g. by cladding walls and/or ceilings with sheets, blocks or tiles of thermally insulating material, by fitting double glazing in window apertures, by laying thermally insulating material in loft floors or by introducing insulation into wall or roof cavities.
The provision of insulation in a roof cavity between inner and outer layers of a sloping roof, e.g. between outer slates or tiles and sarking has generally been achieved hitherto by directing ureaformaldehyde foam into the roof cavity. Although this has resulted in the provision of adequate thermal insulation, the presence of formaldehyde, which is widely acknowledged to have undesirable toxicological properties, in the foam is a significant disadvantage.
It is known, e.g. from W. German Auslegeschrift No. 1,227,649, to form thermally insulating material from cellular polystyrene particles bound together using a synthetic polymer latex binder such as polyvinylacetate and its copolymers. British patent application No. 29873/77 and the corresponding Belgian Patent No. 868,747 discloses the use of such a material as a cavity wall insulation, wherein in order for the material to possess fire retardant properties as required by various laws and local regulations in different countries, an organic bromine-containing compound is incorporated as a flame retardant component in the material. Furthermore it is preferred that the polystyrene particles themselves contain an additive to render them self extinguishing.
Lightweight concretes are known in which expanded polystyrene particles are bound into a solid concrete matrix with cement, for example as described in U.S. Pat. No. 3,764,357. The concrete may if desired contain amounts of an aqueous emulsion of an organic binder, e.g. a copolymer of polyvinylacetate and vinylchloride, to assist in wetting of the expanded polystyrene particles and it may additionally contain less than 30% based on the weight of cement of fly ash (see column 5, lines 54 to 55 and column 7, lines 8 to 9 of U.S. Pat. No. 3,764,357) as a strengthening additive. Although such lightweight concretes are strong materials, since they are concretes they are rigid and relatively brittle materials compared with thermally insulating materials in which cellular polymer particles are bound together by a synthetic polymer latex binder.